Power window devices of motor vehicles comprise, according to the current state of the art, an electric motor (or a manually operated crank handle) that drives a pulley causing driving cables to be pulled thus making a sliding fastening device to be slid. Said sliding fastening device is moved along a guide forcing the window pane to be driven upward or downward through the corresponding guides and joints fitted in the door or frame of the vehicle door.
Fastening devices in conventional power window devices are usually formed by a body provided with a main fastening tab auxiliary fastening tabs formed in a staggered position at the upper portion thereof. Between said tabs, the lower end of the window pane is housed, which is anchored as stated below.
Said main fastening tab includes a protrusion fitted into a hole formed at the lower end of the window pane with the purpose of being coupled therein and being forced to be moved upward or downward together with the fastening device.
The hole in the window pane is usually an elongated hole and in general it is usually bigger in size than the protrusion with the purpose of speeding up the assembly of the window pane in the power window device.
There exist fastening devices for window panes in power window devices of motor vehicles having an improved configuration in which longitudinal flanges are provided, at the upper portion of the fastening device body, formed at both sides of the main fastening tab defining, between them and said body upper portion, respective housings for receiving a cylindrical elastic member (an elastomeric member made by extrusion) extending in a strip projecting outwards from each housing extending on the upper portion of each flange on which the end of the window pane rests.
Although this type of fastening device of the lower end of the window pane has been an effective solution for window pane movement, it is a solution which costs may be reduced by modifying its configuration and consequently its production process. Another of the disadvantages of the fastening devices in known power window devices is that the configuration of the tabs does not show a suitable mechanical strength during the power window device operation.